This invention primarily concerns the packaging of food, particularly meat but is applicable to packaging other articles or items. The invention was made during attempts to make improved xe2x80x9cfreezer bagsxe2x80x9d for repackaging and freezer storing uncooked red meat by the xe2x80x9cconsumerxe2x80x9d in a manner that reduces so called xe2x80x9cfreezer burnxe2x80x9d. However, various aspects of the invention also apply to the xe2x80x9ccommercialxe2x80x9d packaging or repackaging of food, such as by a supermarket or by butchers at a slaughterhouse. Other aspects of the invention include methods for preparing the improved freezer bags; methods for using the bags; the packages of meat; and certain types of thermoplastic film being particularly suitable for use as meat-contacting packaging material.
Reclosable Plastic Storage bags are extremely old in the art. Today, plastic bags are typically available to the public in cartons identified for specific recommended xe2x80x9cend usexe2x80x9d (such as Storage Bags, Heavy Duty Freezer Bags, Vegetable Bags, Trash Bags). Often the bag itself is labeled by xe2x80x9cend usexe2x80x9d, for example, xe2x80x9cZIPLOC(copyright) BRAND Heavy Duty Freezer Bagsxe2x80x9d.
The term xe2x80x9cFreezer Bagxe2x80x9d is hereby defined as a bag having significant functional utility in the storage of food in a freezer. xe2x80x9cFreezer Bagsxe2x80x9d are typically available in the following sizes: 2 gallon (7.6 L); 1 (3.8 L) gallon; pleated xc2xd gallon (1.9 L); quart (0.9 L); and pint (0.5 L).
The term xe2x80x9cFreezer Burnxe2x80x9d is hereby defined as the name for the dehydration that occurs when unpackaged or improperly packaged food is stored in the low humidity atmosphere of a freezer (see xe2x80x9cPackaging Foods With Plasticsxe2x80x9d, by Wilmer A. Jenkins and James P. Harrington, published in 1991 by Technomic Publishing Co., Inc., at page 305).
Freezer burn has remained a major complaint among consumers despite the commercial success of thick plastic freezer bags. In the short-term, freezer burn can be a reversible process. In the long-term, however, freezer burn causes a complex deterioration of food quality involving undesirable texture changes followed by chemical changes such as degradation of pigments and oxidative rancidity of lipids. Taste, aroma, mouth feel and color can all be ruined. Freezer burn of raw red meat is particularly critical because of its impact upon the color of the meat.
Aforementioned xe2x80x9cPackaging Foods With Plasticsxe2x80x9d provides an excellent state of the art summary, with all the information on (commercial) xe2x80x9cpackaging fresh red meat collected in Chapter Sevenxe2x80x9d. Curiously, the book does not appear to mention freezer burn, apart from defining it in the glossary.
xe2x80x9cKeeping Food Freshxe2x80x9d is the title of an article in xe2x80x9cConsumer Reportsxe2x80x9d, for March, 1994, at pages 143-147. The article is too recent to be available as prior art to the extent that this application designates the United States. Nevertheless its contents are of interest in showing the absence of certain types of prior art, and therefore enhancing the patentability of the present invention.
The xe2x80x9cConsumer Reportsxe2x80x9d article attempts to answer the question as to which packaging material (plastic, aluminum, waxed paper, bags, wraps or reusable containers) do the best job of (1) keeping food fresh for xe2x80x9cthe long haulxe2x80x9d, (2) at lowest overall cost, and (3) with minimum adverse environmental impact. It xe2x80x9ctop ratesxe2x80x9d ZIPLOC(copyright) Pleated Freezer Bags (at page 145). It points out that food stored in plastic containers can suffer from freezer burn if the container contains too much air. Concerning xe2x80x9cwrapsxe2x80x9d (plastic films and freezer papers) it advised against double wrapping because of cost and environmental reasons and xe2x80x9cour tests showed that double wrapping doesn""t afford much extra protection anywayxe2x80x9d. Nowhere does the article disclose or suggest the invention described hereinafter.
The patent literature contains descriptions of various types of bags having liners or double walls including some space between the walls. Some of these patents relate to the transportation and storage of food. U.S. Pat. No. 4,211,091 (Campbell) concerns an xe2x80x9cInsulated Lunch Bagxe2x80x9d. U.S. Pat. No. 4,211,267 (Skovgaard) describes a xe2x80x9cCarrying Bagxe2x80x9d for xe2x80x9cgetting home with frozen food before it thawsxe2x80x9d. U.S. Pat. No. 4,797,010 (assigned to Nabisco Brands) discloses a duplex paper bag as a xe2x80x9creheatable, resealable package for fried foodxe2x80x9d. U.S. Pat. No. 4,358,466 (assigned to The Dow Chemical Company) relates to an improved xe2x80x9cFreezer To Microwave Oven Bagxe2x80x9d. The bag is formed of two wing shaped pouches on each side of an upright spout. U.S. Pat. No. 5,005,679 (Hjelle) concerns xe2x80x9cTote Bags Equipped With A Cooling Chamberxe2x80x9d. All of these food bags appear to have very thick food contacting walls compared to the invention described hereinafter. None of these patents appear to focus on freezer burn.
Books on xe2x80x9cHome Freezingxe2x80x9d are of interest to this invention. Concerning xe2x80x9cWrapping Meat for the Freezerxe2x80x9d, the book xe2x80x9cRodale""s Complete Book of Home Freezingxe2x80x9d by Marilyn Hodges and the Rodale Test Kitchen staff (1984) suggested the inconvenient method of wrapping meat chunks in a single layer of freezer paper and xe2x80x9csucking out the air with a strawxe2x80x9d (trying to avoid getting blood into ones mouth) in order to reduce the amount of dehydration in the freezer (see page 173).
There is clearly still a great need to improve existing methods of packaging fresh meat, as determined by consumer surveys, coupled with the fact that there is a 45 billion dollar retail market in the U.S. alone, consuming about 225 million dollars worth of plastic packaging materials annually.
In contrast to the known prior art, it has now been surprisingly discovered that certain types of multiple walled plastic bags (defined herein as xe2x80x9cmultibagsxe2x80x9d) are better than corresponding single wall freezer bags (having equal or greater weight than the multiple walled bags) for use as a functional freezer bag for preserving red meat without freezer burn. All of the independent claims hereinafter concern different but related broad aspects of the invention, and are hereby incorporated by reference.